PROSITE documentation PDOC51369 [for PROSITE entry PS51369]

TCP domain profile

The TCP domain has been named after its first characterized members (TB1, CYC and PCFs). So far, members of the TCP family have only been found in plants and function in processes related to cell proliferation. The TCP domain is probably involved in DNA-binding and protein-protein interactions [1].

The TCP domain is predicted to form a non-canonical basic-Helix-Loop-Helix (bHLH). The main conserved features of the TCP domain are: two short stretches of residues in the basic region, hydrophobic residues along the apolar face of both α-helices, a tryptophan in helix II, and a helix-breaking glycine in the loop between the helices. However the residues in the loop and the hydrophilic residues of the helices are not as well conserved. TCP domains form two subfamilies: one closely related to CYC and TB1, and another more related to the PCFs. The basic region of the CYC/TB1 subfamily contains a putative bipartite nuclear localization signal (NLS) (see <PDOC00015>) while the basic region of the PCF subfamily contains only a portion of a bipartite NLS [1].

Some proteins known to contain a TCP domain are listed below:

• Antirrhinum majus cycloidea (cyc). It is involved in the control of floral symmetry, a character that has changed many times during plant evolution.
• Maize teosinte branched 1 (tb1). It controls developmental switches that contributed to the evolution of maize from its wild ancestor teosinte.
• Rice PCF1 and PCF2, proteins that may bind to DNA as homo- or heterodimers. These proteins were isolated on the basis of their ability to bind specifically to promoter elements of the rice gene for the proliferating cell nuclear antigen, PCNA, a protein involved in DNA replication and cell cycle control.
• Arabidopsis thaliana TCP2 and TCP3, which correlate with actively dividing regions of the floral meristem.

The profile we developed covers the entire TCP domain.